1. Field
One or more embodiments of the present invention relate to an organic light-emitting device. In particular, one or more embodiments of the present invention relate to an organic light-emitting device with high emission efficiency including a mixed organic layer and an electron transport layer.
2. Description of the Related Art
Organic light-emitting devices generate light by a recombination of electrons and holes in an organic layer interposed between electrodes when a current is applied to the organic layer. Accordingly, organic light-emitting devices enable a lightweight, thin information display device to be embodied, which has a short response speed and a wide viewing angle while producing a high quality image. Due to these advantages, techniques for organic light-emitting devices have rapidly developed, and organic light-emitting devices are used in a wide range of applications from mobile phones to high-quality information display devices. In order to develop an organic light-emitting device in terms of yield and quality, emission efficiency and lifetime need to be increased while lowering power consumption.
As for doping a hole transport layer of an organic light-emitting device, according to a conventional technique, a hole injection layer and/or hole transport layer is doped with tetrafluoro tetracyano quinodimethane (F4TCNQ) or the like to reduce power consumption. However, the molecular weight of the compound is too low and thus, chamber contamination may occur during a deposition process and an emission efficiency of an emission layer may be degraded.
In order to prevent expression of dark spots or pixel shorts due to foreign substances remaining on the surface of a substrate during the manufacture process of an organic light-emitting device, the thickness of a hole transport layer needs to be 500 Å or more. In this case, however, holes may not be smoothly transported to an emission layer and thus, an operating voltage of an organic light-emitting device is increased and the efficiency and lifetime of the organic light-emitting device is lowered. Accordingly, there is a need to decrease an operating voltage which directly affects power consumption when an organic light-emitting device is manufactured.
Conventionally, an electron transport layer is formed by doping an organic material with an alkali metal such as lithium or cesium. However, an electron transport layer formed as described above may have low efficiency or a short lifetime.